


the scientific method

by minycrds



Category: Haikyuu!!
Genre: Domestic Fluff, Fluff, Fluff and Smut, It's not important im just obsessed with sakusa in lingerie, Lingerie, M/M, petnames, this fic is for me and for me only, this is just an excuse for atsumu to call sakusa princess during sex im not gonna lie
Language: English
Status: Completed
Published: 2021-03-11
Updated: 2021-03-11
Packaged: 2021-03-18 12:08:57
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,436
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29982651
Author URL: https://archiveofourown.org/users/minycrds/pseuds/minycrds
Summary: Miya Atsumu is kinda new at this whole relationship thing. Sure, he’s had a couple of friends with benefits who he’s grown too comfortable around for some time and one or two flings that got too attached. The issue wasn’t commitment here, the issue was the sensation he felt expanding in his chest every time he woke up before Kiyoomi and witnessed his slurry morning and his almost hungry huffs at him for breathing too loudly.And suddenly, it hit him.The closest they’d ever been to using pet names was using an abbreviation of the other’s name and Atsumu had an inkling Kiyoomi wouldn’t be against it.-Atsumu comes up with a stupid plan to find out if Omi likes pet names.
Relationships: Miya Atsumu/Sakusa Kiyoomi
Comments: 6
Kudos: 159





	the scientific method

Miya Atsumu is kinda new to this whole relationship thing. Sure, he’s had a couple of friends with benefits who he’s grown too comfortable around for some time and one or two flings that got too attached. The issue wasn’t commitment here, the issue was the sensation he felt expanding in his chest every time he woke up before Kiyoomi and witnessed his slurry _morning_ and his almost angry huffs at him for breathing too loudly. So Atsumu had learnt how to stay real quiet and still in the mornings just so his Omi could get the hours he claimed was the healthiest amount of sleep someone could get. Well, at least this relationship was fixing his sleeping schedule.

Atsumu knew Kiyoomi didn’t know much about relationships either. Although neither of them were experienced, while Atsumu’s uncertainty laid on his inability to know what was too little and too much for something as new as what they had, Sakusa’s discomfort had more to do with his failed non-relationships in the past thanks to his lack of common sense rather than anything else. 

Both of them were trying hard and both of them were awkward at best at the beginning, but had learnt to master what they struggled. And so things had gotten comfortable between them. Good, very good.

There was one thing Atsumu couldn’t master, though. And he would’ve noticed before if he hadn’t had such a special place in Kiyoomi’s heart which meant that he was allowed to call him Omi, while almost everyone else had to stick to _Sakusa-san_ to humor him and keep things civil. 

He wasn't even sure he would’ve noticed hadn’t his twin brother and _sadly_ , Atsumu’s kind of best friend for life, Suna Rintarou had shown up to his house with beers and food in their hands. There would’ve been no issue whatsoever hadn’t Sunarin grown clingier the drunker he got and hadn’t Kiyoomi been completely sober. 

The night went on with an assortment of _babe, baby, honey, dear, darling, sweetheart, peach_ and a whole lot more he’d rather forget for the rest of his life. Osamu’d blushed lightly and jabbed at Rin’s ribs to make him stop, which only further encouraged him to keep embarrassing everyone around him as he so much enjoyed. Atsumu knew this was a new development, because both of them had always stuck to first names and the casual babe here and there, but never anything past that. 

Atsumu did _absolutely not_ have a problem with this, really. None, even as he gritted his teeth and yelled at Osamu to please make him stop. The problem was Sakusa, who sat there in front of them hiding his amused smile and creeping blush behind his non-alcoholic beer. 

And suddenly, it hit him. 

The closest they’d ever been to using pet names was using an abbreviation of the other’s name and Atsumu had an inkling Kiyoomi wouldn’t be against it. 

He formulated a plan in his head. 

Step one: Look for a list of pet names he was to try with Kiyoomi. They were separated in three categories. One, appropriate for the public. Two, appropriate at home during domestic moments. Three, sex only pet names. 

Step two: Surprise Omi with one or two to test his reaction. He would write down each of them and maybe use them on more than one occasion to make sure he understood their effect on the subject. He wanted to pick only the ones Omi enjoyed and save the rest to be annoying. 

Step three: Improvise? He wasn’t really good at this whole thing. He was sure he always did terribly in science and Samu was always saving his ass.

Well then. 

He conducted his research mostly on his phone while he waited for coffee one morning after a good jog and shower. Sure, it wasn't the best idea but he was so used to sleeping with Kiyoomi that sleeping by himself when Kiyoomi went home was weird and he had trouble sleeping. They should definitely discuss moving in together what with all the time they spent together anyways— Back to the plan.

He wrote a list on the notes app, switching between the ridiculous amount of articles he'd pulled from Google in his browser and the too-long-list he'd created. Now onto categories.

* * *

The moment came unexpectedly when he was buried to the hilt in Kiyoomi's ass on a lazy Sunday morning. He didn't think too much about it. In fact, he'd gone over the list so many times he was sure he'd memorised most of it already. Plus, it was Sunday morning, he hadn't even brushed his teeth before he'd started lazily grinding on Kiyoomi's ass, yet somehow, here he was, moving slowly in shallow thursts behind the impatient and imposing figure of his boyfriend completely relaxed resting on his side. 

His right hand previously squished somewhere between the pillows and Omi's shoulder was now making its way to his chest in order to hold him closer to him. Finally, Kiyoomi scooted back a little, allowing Atsumu's lips to easily find the usual spot on his neck that he liked so much and knew made Omi shudder. His left hand held his left hip in place to make sure his boyfriend didn't have to do a thing, but he was thinking of maybe reaching for his cock too. He wasn't so sure about that, after all, they'd woken up only a few minutes ago and Atsumu's limbs felt too heavy to use even more energy than he already was. Omi wouldn't kill him for neglecting him a little during lazy sex and he'd be mad if they stained the freshly changed sheets. Oh, but the lube had already— Damn. 

Either way, Atsumu was in a state of bliss. The kind you can only reach when the sun is shining on you and your stupidly athletic and gorgeous boyfriend and you're balls deep in his ass and you just paid your bills and you know life is _good_. 

And so when he finally felt like he could manage to move a little more, he reached for Kiyoomi's cock, automatically eliciting a punchy and nasal unexpected moan. The list didn't even come to mind and it just happened naturally.

" _Babe, baby,_ you feel so good," he whispered in lieu of his usual _Omi_ , lips still attacking his neck and he finally started thrusting into him with more effort. 

Kiyoomi didn't particularly react to it and Atsumu took it as a good sign to consider it out of bed as well. First two, done. 

He used it during lunch when asking for the low sodium salt and he was able to see how Kiyoomi's lip trembled just a little and his ears reddened. He held in an incoming giggle and decided his method was definitely working. He was totally getting good at this whole commitment thing. 

When it came to the rest of the list he wasn't so sure how to approach it, really. Would Kiyoomi even like being called _darling, sweetheart, love_ and the most anticipated one he'd scratched and rewritten five times before saving the list?

Atsumu was having issues with dropping the pet names casually into conversation and he was having trouble getting the full reaction from Kiyoomi. It was obvious Kiyoomi hated some of them, but he mostly got flustered when Kiyoomi tried a new one. For example, when he finally had the guts to try calling him sweetheart, Atsumu was laying on Kiyoomi's chest, both sprawled on the couch with a shitty reality TV show playing. He was simply too comfortable to move and so he'd asked, amused, " _Sweetheart, can you hand me the water bottle?_ and he'd felt Kiyoomi's heartbeat increase right then and there. Kiyoomi tensed for a second under him, pursed his lips and made no sound as he stretched his arm to pass him the bottle of water. Atsumu had replied only with a wink and a click of his tongue and he could already see him blushing a little. 

Truth be told, Atsumu wasn't really expecting his stupid plan to work, given how he'd ignored most of it in favour to using what he believed were the most appropriate moments to use the categories he'd established, but really, could you expect a man not to call Sakusa Kiyoomi _babe_ after an absolutely brutal serve in the privacy of their little corner of the court? Sakusa would argue they in fact did not own any corner of said court, seen as how Inunaki and Adriah had choked on their spit and laughed behind their backs until Kiyoomi gave them the deadliest glare. Unfortunately, for everyone involved in the incident, Kiyoomi did not forget and made sure to victimise each of them with his spikes as much as he could for the entirety of a week. 

Of course, that did not mean Atsumu stopped calling him _babe_ at home and Kiyoomi was actually responding to it now. It was nice.

The next name on the list was one of Atsumu's favourite because of how cheesy it was, but the moment he called Kiyoomi _his sweetpea_ , the glare he got back meant more than words could ever express. He was fine with it, given how he had already tested _darling_ and _angel_ and those seemed to work only in bed when Kiyoomi was sleepy and needed cuddles. What a fucking baby. 

The rest of the list went like this: 

" _Love,_ Samu invited us for dinner, do you wanna go?," yelled from the bathroom to the kitchen where Kiyoomi was drinking his coffee, only to give him a couple of seconds to turn as red as a tomato. Atsumu heard him choke on the liquid and snickered in the bathroom before leaving to pretend he'd had no double intentions. Kiyoomi had only nodded, managing to look somehow both flustered and stoic as he scrolled down his phone to try and find a distraction.

"Honey," that one felt wrong from the very start. He stopped himself before continuing and Kiyoomi just stared at him, before Atsumu decided to continue with his usual stupid ideas, "We should get some honey, don't you think," and then he stopped, unable to swallow the upcoming cackle as he attempted to articulate,"love of my life". He squeaked when Kiyoomi left the pasta aisle abruptly, huffing and utterly horrified at Atsumu's sheer audacity. He'd been silent the entire way home and had made Atsumu carry all the groceries up the five fights of stairs. 

And then there were the ones he knew would horrify Omi even more, but he'd considered very interesting such as: pumpkin, sweetie pie, muscleman, hottie, buddy and _baby cakes_. Kiyoomi had made an official request, serious conversation in the couch and all, to please stop whatever he was doing. Atsumu had used his best puppy eyes and had replied " _but, baby cakes, I'm not doing anything"._ Kiyoomi had shut the door on his face and made him walk back to his own place after that. 

The last name in the list haunted him, he could feel it glaring at him every time he opened the notes app. The experiment had long finished and Kiyoomi seemed to enjoy being called babe and darling the most and when he felt adventurous enough he even called Atsumu baby. Not gonna lie, Atsumu absolutely melted every time that happened because he was after all, nothing but a weak man. 

The moment came once again very similarly to the first one. Or at least his dick was in the same place.

Everything else was different, but hey, give him some credit. It absolutely was not Atsumu's fault this time. 

Kiyoomi was different. Unlike the first time he'd used the word _babe_ to refer to him, Kiyoomi's full attention was on Atsumu. He had him pressed into the mattress on his back, one hand splayed on his chest as he reached for the lube with the other. He looked sinful on top of Atsumu, wearing nothing but the most ridiculous white lace bralette that was too little for his tits and matching panties, envelopped in the soft peachy colour in the sky that came from the window and reflected in the white walls of his bedroom. Then, he stood on his knees, one on each side of Atsumu as he reached behind to finger himself.

Atsumu's mouth watered at the sight. 

One of his hands reached for his hips to help him find a rhythm while he fingered himself and the other massaged his length through the soft fabric. He hissed through his teeth at the wet patch in Kiyoomi's panties. God, he wished he could see Kiyoomi's fingers slowly fucking into his ass in those pretty panties but Kiyoomi did not seem in the mood to move from the position they were in and Atsumu was no one to complain in this situation, really. 

Kiyoomi held him down while he sat on his cock, taking his sweet time as he went down. Atsumu's thighs tensed and shivered with the effort to stay still while his boyfriend fucked himself on his cock. It was an absolute sight.

His hands roamed all over Kiyoomi's body, scratching at his thighs and pressing down on his cock with the palm of his hand to give him some friction when he managed to get ahold of himself. Fuck, he was getting close. 

" _Babe,"_ he whispered into the bedroom, chest heaving as Kiyoomi moved faster, "you look like you were made to sit on my cock". 

Kiyoomi moaned in reply and finally reached into his panties to take his cock in hand and slide his fist up and down. Atsumu planted his feet on the bed, finally able to meet Kiyoomi's hips and thrust into him. The rhythm was sloppy at best and Atsumu was positive he looked absolutely wrecked anyway. He sat up to reach for Kiyoomi, arms wrapping around him as his lips met his in an almost furious kiss. Finally, Kiyoomi stilled and let Atsumu fuck him at his own devastating pace. 

"You're gonna kill me. You take me so well, _princess_. Feel so good," Atsumu moaned, face buried in the crook of Kiyoomi's neck as he jolted with every one of Atsumu's thrusts. 

Atsumu continued encouraging him to come with a combination of _Omi, baby, babe_ and the so dreaded _princess._ Kiyoomi came hard, ruining his panties, still in Atsumu's arms and once they came down Atsumu smiled big and bright to the ceiling

"So, princess. That's the one?" He asked in amusement.

"Shut up, Atsumu". 

**Author's Note:**

> i wrote this in an hour don't judge me and i've no idea what this writing style is i feel like atsumu's spirit just possessed me


End file.
